Britain's transport network began to buckle as heavy snow swept the UK.

Flights were cancelled at the country's busiest airport while train companies axed rail services and roads were closed as the wintry conditions set in.

Motorists were urged to avoid all but essential journeys amid strong winds, plunging temperatures and the looming threat of blizzards. Forecasts also forced hundreds of schools to shut their doors, meaning some sixth-form and college students saw their A-level exams postponed.

The adverse weather has already sparked panic-buying and left more than 10,000 people without electricity.

Weathermen predict around 12in (30cm) of snow will fall in some areas during the next few hours while gusts could reach galeforce of 40-45mph around Scottish isles. Temperatures are expected to remain close to freezing throughout the day after dropping to -8 in the Highlands overnight.

The Met Office has issued a "red" severe weather warning for heavy snow in Wales, which is set to experience the worst of the snow. Amber alerts were in place for the Midlands, London and the South, the east of England, the South West, the North West and Northern Ireland.

The arctic blast closed Cardiff airport and led Heathrow to shut one runway for de-icing and snow-clearing, prompting delays and cancellations. The airport has already pulled around 70 flights. A statement on Gatwick's website warned passengers to check before leaving their homes.

Rail travellers also experienced upheaval as operators scrapped services. Eurostar axed four trains between London and Brussels while South West Trains announced cancellations. The East Midlands, Greater Anglia and Southern companies were running amended timetables.

Poor conditions also caused severe hold-ups on the roads. Cardiff city centre became a sludgy bumper-to-bumper convoy of commuters as some braved the conditions while other usually busy routes were empty of cars. The AA expected most disruption in Wales, the West Midlands, southern England and Northern Ireland.

RAC spokesman Simon Williams said reaching stranded motorists was now a "real challenge". "We moved a number of our 4x4 patrols to help people stuck in the snow in West Wales and parts of Wiltshire, South Gloucestershire and Hampshire," he said. "In order to deal with an expected increase in calls for assistance later in the day, we have also put every technically qualified engineer normally based in the office back out on the road again in patrol vehicles."